This program project is directd towards elucidating the pathophysiology of thrombosis by developing new assays which reflect activation of hemostasis and applying these in physiologic investigation in vitro and in studies of patients with thrombosis. In previous work technologies used included purification of peptides, amino acid analysis and sequencing and solid phase peptide synthesis. Using these techniques specific and sensitive radioimmunoassays were developed for fibrinopeptide A and desarginine fibrinopeptide B (respectively indicating fibrin I and II formed by thrombin proteolysis of fibrinogen). Beta 1-42 (indicating fragment X formed by plasmin proteolysis of fibrin I), platelet factor 4 and Beta-thromboglobulin (indicating platelet alpha granule release). Application of the assays to studies of patients with disseminated intravascular coagulation, venous thromboembolism and coronary artery disease have led to new concepts of the sequence and regulation of proteolyses in disseminated intravascular coagulation and in venous thrombosis. With the assistance of new technologies including high performance liquid chromatography, the hybridoma technique for raising monoclonal antibodies and vascular endothelial cell tissue culture, major efforts are underway to develop assays for antigens specific to the endothelial cell, for the Alpha chain and Gamma chain cross-links of fibrin and for mapping the AAlpha chain of fibrinogen. The new assays will be used in addition to those previously developed, to investigate the biochemistry and physiology of fibrinogen proteolysis and platelet Alpha granule release in purified systems and in whole blood. Detailed analysis will be made of the fibrin and platelet protein content of thrombi and emboli obtained at surgery and autopsy. The interaction of platelets and coagulation factors with cultured endothelial cells will be explored. Clinical studies will include disseminated intravascular coagulation in obstetrical patients and in patients with acute leukemia. The effect of intermittent compression of the blood changes associated with venous thrombosis will be determined. Detailed correlations will be made between hematological changes and angiographic findings in acute myocardial infarction and after angioplasty for peripheral vascular disease as well as in carotid atherosclerosis. Hence new technologies are being used with direct application to diseases of considerable public health importance.